1. Field of the Invention
The present invention relates to a display panel, a display device having the display panel, and a method of detecting touch position on the display device. More particularly, the present invention relates to a display panel capable of performing a touch screen function, a display device having the display panel, and a method of detecting the touch position on the display device.
2. Description of the Related Art
In general, a display device is a device that displays an image so that a user recognizes processed information that is processed by a processing unit. A flat panel display device has various characteristics such as a relatively small size, a relatively lightweight structure, and a relatively high resolution, etc., so that the flat panel display device has been widely used.
One type of flat panel display device is a liquid crystal display (“LCD”) device that is most widely used in various fields. The LCD device displays the image using liquid crystals. Liquid crystals vary arrangement in response to an electric field applied thereto, and thus a light transmittance of the liquid crystals is changed.
The LCD device includes an LCD panel. The LCD panel includes an array substrate having a thin film transistor (“TFT”) that is a switching element, an opposite substrate facing the array substrate, and a liquid crystal layer interposed between the array substrate and the opposite substrate.
The LCD device, in general, includes an input part having a control interface and a system part that calculates data to output a control signal. The data is applied to the system part through the input part. The LCD device displays the image through a one-way communication using the control signal.
The LCD device can further include a touch panel that receives data using icons displayed on a screen of the LCD device so that the user can directly input the data to the LCD panel.
The touch panel is on an uppermost portion of the LCD device to make contact with a finger or a touching object so that the user selects information displayed on the screen of the LCD device. The touch panel detects a touch position on which the finger or the touching object makes contact with the screen, and changes the touch position into an input signal to apply the input signal to the LCD device. When a computer includes the LCD device having the touch panel, an additional input part such as a keyboard, a mouse, etc., is unnecessary. In addition, in a mobile device such as a cellular phone including the LCD device having the touch panel, an additional input part such as a keypad is unnecessary. Thus, the touch panel has been widely used.
When the touch panel is formed on the LCD panel, a thickness and a size of the LCD device having the touch panel is increased. In order to decrease the thickness and the size of the LCD device, the touch panel is integrally formed with the LCD device. For example, the LCD device includes a photo sensor that detects a shadow formed by the finger or the touching object blocking the light when touching the touch panel or detects additional light generated from a light pen touching the touch panel.
However, when the LCD device includes the light sensor, an amount of the light sensed by the light sensor is dependent on an amount of an ambient light. That is, when the amount of the ambient light is increased, the amount of the light sensed by the light sensor is increased. Also, when the amount of the ambient light is decreased, the amount of the light sensed by the light sensor is decreased. Therefore, sensing capability of the light sensor is deteriorated so that the touch panel does not detect the touch position of the finger or the touching object.